Synthesis and antimuscarinic properties of quinuclidin-3-yl 1,2,3,4-tetrahydroisoquinoline-2-carboxylate derivatives as novel muscarinic receptor antagonists

Article abstract of DOI:10.1021/jm050099q

In the course of continuing efforts to develop potent and bladder-selective muscarinic M₃ receptor antagonists, quinuclidin-3-yl 1-aryl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate derivatives and related compounds were designed as conformationally restricted analogues of quinuclidin-3-yl benzhydrylcarbamate (8). Binding assays with rat muscarinic receptor subtypes revealed that the quinuclidin-3-yl 1-aryl-1,2,3,4- tetrahydroisoquinoline-2-carboxylate derivatives showed high affinities for the M₃ receptor, and selectivity for the M₃ receptor over the M₂ receptor. Of these derivatives, (+)-(1S,3'R)-quinuclidin-3'-yl 1-phenyl-l,2,3,4-tetrahydroisoquinoline-2-carboxylate monohydrochloride (9b) exhibited almost the same inhibitory activity against bladder contraction to that of oxybutynin (1), and more than 10-fold selectivity for bladder contraction versus salivary secretion, demonstrating that 9b may be useful for the treatment of symptoms associated with overactive bladder without having side effects such as dry mouth.

Full text of DOI:10.1021/jm050099q

J. Med. Chem. 2005, 48, 6597-6606
6597
Synthesis and Antimuscarinic Properties of Quinuclidin-3-yl
1,2,3,4-Tetrahydroisoquinoline-2-carboxylate Derivatives as Novel Muscarinic
Receptor Antagonists1
Ryo Naito,* Yasuhiro Yonetoku, Yoshinori Okamoto, Akira Toyoshima,† Ken Ikeda, and Makoto Takeuchi
Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
Received February 2, 2005
In the course of continuing efforts to develop potent and bladder-selective muscarinic M3 receptor
antagonists, quinuclidin-3-yl 1-aryl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate derivatives and
related compounds were designed as conformationally restricted analogues of quinuclidin-3-yl
benzhydrylcarbamate (8). Binding assays with rat muscarinic receptor subtypes revealed that
the quinuclidin-3-yl 1-aryl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate derivatives showed high
affinities for the M3 receptor, and selectivity for the M3 receptor over the M2 receptor. Of these
derivatives, (+)-(1S,3’R)-quinuclidin-3’-yl 1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate
monohydrochloride (9b) exhibited almost the same inhibitory activity against bladder contrac-
tion to that of oxybutynin (1), and more than 10-fold selectivity for bladder contraction versus
salivary secretion, demonstrating that 9b may be useful for the treatment of symptoms
associated with overactive bladder without having side effects such as dry mouth.
Introduction
Muscarinic receptor antagonists including oxybutynin
(1)2 are mainly used in the treatment of urinary
frequency, urinary incontinence, or urgency associated
with overactive bladder (OAB). However, treatment
with muscarinic antagonists is well-known to be associ-
ated with a variety of systemic side effects, such as dry
mouth, constipation, mydriasis, and tachycardia,3 re-
sulting from their nonselective antimuscarinic effects.
Tachycardia is caused by blockage of muscarinic M2
receptors in the heart, and dry mouth, constipation, and
mydriasis occur due to the blockage of M3 receptors in
the salivary glands, the colon and the pupil, respec-
tively. Among these side effects, dry mouth most
frequently limits the use of these agents. Consequently,
muscarinic receptor antagonists with subtype selectivity
for the M3 receptor over the M2 receptor and bladder
selectivity would be useful for treatment of OAB. Hence,
distances between the benzene rings and the nitrogen
many studies aimed at discovery of subtype-selective or
atom in the basic ring in compounds 6 and 7 were
tissue-selective muscarinic receptor antagonists have
been reported, including those on tolterodine (2),4
darifenacin (3),5 KRP-197 (4),6 and 5.7
In two previous reports, we have described two series
of carbamate derivatives, benzhydrylcarbamates8 and
biphenyl-2-ylcarbamates,9 as novel bladder selective
muscarinic M3 receptor antagonists. Among these mol-
ecules, YM-58790 (6) and YM-46303 (7) showed good
estimated to be in the range of 6-8 Å from X-ray
selectivity for bladder contraction versus salivary secre-
crystallographic and modeling studies, similar to the
tion in rats, in comparison with oxybutynin (1). Com-
distances reported for atropine and other muscarinic
pounds 6 and 7 have common structural features: a
antagonists.10-12 Our previous SAR studies suggested
hydrophobic region including two benzene rings, a basic
that introduction of the carbamate group at the junction
nitrogen-containing ring, and a carbamate junction. The
resulted in creation of novel and selective M3 receptor
antagonists, and that both the hydrophobic region and
the basic ring influence selectivity for the M3 receptor.
In contrast to 6, which has high affinity and selectivity
for the M3 receptor, quinuclidin-3-yl benzhydrylcarbam-
* To whom correspondence should be addressed. Phone: +81-29-
863-6730. Fax: +81-29-852-2971. E-mail: ryo.naito@jp.astellas.com.
† Present address: Development Division, Astellas Pharma Inc.,
3-17-1 Hasune, Itabashi, Tokyo 174-8612, Japan.
10.1021/jm050099q CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/28/2005

6598 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21
Naito et al.
Scheme 2a
Figure 1. Design of quinuclidin-3-yl 1,2,3,4-tetrahydroiso-
quinoline-2-carboxylate derivatives (9-16).
Scheme 1a
a Reagents and conditions: (a) POCl3, P2O5, xylene, reflux; (b)
NaBH4, EtOH, rt.
a Reagents: (a) (+)- or (-)-tartaric acid; (b) recrystallization;
(c) aq NaOH; (d) (+)- or (-)-mandelic acid; (e) (+)- or (-)-DIBETA.
ate (8) showed poor selectivity among the muscarinic
receptor subtypes.8 On the other hand, quinuclidin-3-
yl and -4-yl 2-biphenylylcarbamate derivatives, includ-
ing 7, showed high affinities and selectivities for the M3
receptor,9 suggesting that proper arrangement of the
two aromatic rings in the hydrophobic part of the
molecule can improve subtype selectivity. We therefore
hypothesized that restricting the conformation of the
benzhydrylcarbamate moiety in 8 could lead to an
increase in selectivity for the M3 receptor over the M2
receptor. Hence, in the course of continuing research to
develop potent and more bladder-selective muscarinic
M3 receptor antagonists, quinuclidin-3-yl 1-aryl-1,2,3,4-
tetrahydroisoquinoline-2-carboxylate derivatives and
related compounds were designed based on this hypoth-
esis. These compounds were synthesized and evaluated
for their affinities toward rat muscarinic receptors, and
the effects of the stereochemistry of the substituent at
the 1-position of the tetrahydroisoquinoline ring on
affinity and subtype selectivity were investigated. We
were also particularly interested in the influence of this
modification on the selectivity for bladder contraction
versus salivary secretion. Herein, we report the syn-
thesis, structure-activity relationships, and pharma-
cological evaluation of this series of muscarinic M3
receptor antagonists.
and 4-hydroxy-1-phenyl-1,2,3,4-tetrahydroisoquinolines
(cis-29 and trans-29),20 were carried out according to
the reported methods.
The (R)- and (S)-quinuclidin-3-yl carboxylate deriva-
tives (9-16) were prepared from the 1,2,3,4-tetrahydro-
isoquinolines (22-26, 28, and 29) and isoindoline (27)
via ethyl carboxylate derivatives (Method A) or directly
(Method B), as shown in Scheme 3. The 1,2,3,4-tetra-
hydroisoquinolines [22, (+)-23, 24 and 28] were treated
with ethyl chloroformate in the presence of potassium
carbonate in dichloromethane. The resulting ethyl
1,2,3,4-tetrahydroisoquinoline-2-carboxylates (30-33)
were reacted with (R)-quinuclidin-3-ol [(R)-34]21 in the
presence of sodium hydride in toluene, with continuous
removal of the ethanol formed, to give (3R)-quinuclidin-
3-yl carboxylates (9, 9a, 9b, 11, 12b, and 13) (Method
A). Using (S)-quinuclidin-3-ol [(S)-34] instead of (R)-34,
(3S)-quinuclidin-3-yl ester derivatives (9c and 9d) was
also prepared. As an alternative method, (R)-quinucli-
din-3-yl carboxylates (10, 12a, 14-16) were prepared
from 1,2,3,4-tetrahydroisoquinolines [(-)-23, 25, 26, and
29] and isoindoline (27) with (R)-quinuclidin-3-yl chloro-
formate monohydrochloride (35)22 in pyridine (Method
B). Some of the diastereomeric (3R)-quinuclidin-3-yl
1,2,3,4-tetrahydroisoquinoline-2-carboxylate derivatives
(13, 14, and 16) were separated using preparative HPLC
to give the desired single diastereomers.
The quinoline-2-carboxylate derivative (39) was pre-
pared as shown in Scheme 4. Hydrogenation of quinaldic
acid (36) in the presence of Raney Ni followed by
esterification gave methyl 1,2,3,4-tetrahydroquinoline-
2-carboxylate (37). Phenylation at the 1-position of
37 was carried out using triphenylbismuthine and
copper(II) acetate.23 The resulting methyl 1-phenyl-
1,2,3,4-tetrahydroquinoline-2-carboxylate (38) was con-
verted to the corresponding quinuclidin-3-yl ester (39)
according to Method A. The absolute configurations of
9b, 12a, and 16d were determined by X-ray crystal-
lography using Bijvoet’s method. The configuration of
16c was also determined relative to the known absolute
configuration of (R)-quinuclidin-3-ol.
Chemistry
The intermediates, 1-substituted 1,2,3,4-tetrahydroiso-
quinolines (22-26), were synthesized using a Bischler-
Nepieralski isoquinoline synthesis from the correspond-
ing N-(2-phenylethyl)carboxamides (17-21), as shown
in Scheme 1.13 Optical resolution of 1-phenyl-1,2,3,4-
tetrahydroisoquinoline (22) was carried out according
to the reported method,14 and 23 and 26 were resolved
by using mandelic acid and dibenzoyltartaric acid
(DIBETA), respectively (Scheme 2). From the report of
Ludwig et al.15 and our X-ray crystallographic analysis
of the hydrochloride salt of (+)-22 using Bijvoet’s
anomalous dispersion method,16 the absolute configu-
ration of (+)-22 is S, although it had previously been
reported that the configuration of (-)-22 is S.17,18 The
syntheses of other intermediates, 1-phenylisoindoline
(27),19 4-phenyl-1,2,3,4-tetrahydroisoquinoline (28),13

Muscarinic Receptor Antagonists
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21 6599
Scheme 3a
a Reagents and conditions: (a) ClCO2Et, K2CO3, CH2Cl2, rt; (b) (R)- or (S)-quinuclidin-3-ol (34), NaH, toluene, reflux; (c) (R)-quinuclidin-
3-yl chloroformate hydrochloride (35), pyridine, <-20 °C-rt.
Scheme 4a
effects of substituents at the 1- and 4-position of the
tetrahydroisoquinoline ring and the influence of
their stereochemistry on affinity and selectivity for the
M3 receptor were investigated. The results are shown
in Table 2. Four diastereomers of quinuclidin-3-yl
1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate
(9a-d) were initially prepared and evaluated. The (3R)-
quinuclidin-3-yl isomers (9a and 9b) showed much
higher affinity for the M3 receptor than the 3S isomers
(9c and 9d). Of the two 3R isomers (9a and 9b), the
(1R)-1-phenyl-1,2,3,4-tetrahydroisoquinoline derivative
(9a) showed over 10-fold higher affinity for the M3
receptor than the 1S isomer (9b), although their selec-
tivity ratios for the M3 receptor over the M2 receptor
were almost the same. Both compounds 9a and 9b
showed almost as high affinities for the M1 receptor
as for the M3 receptor. These results indicate that
modification of the benzhydryl moiety in 8 to form a
1-phenyl-1,2,3,4-tetrahydroisoquinoline ring can lead to
improvement of selectivity for M1 and M3 receptors over
the M2 receptor by decreasing affinity for the M2
receptor. The stereochemistry at both the 3-position of
the quinuclidine ring and the 1-position of the tetra-
hydroisoquinoline ring are of importance in obtaining
high affinity for the M3 receptor.
Next, the effect of substituents at the 1-position of
the tetrahydroisoquinoline ring on affinity and selectiv-
ity for the M3 receptor was investigated. The 3- and
2-thienyl derivatives (12 and 13) showed similar affini-
ties and selectivities for the M3 receptor, compared to
9a and 9b. Among the 3-thienyl derivatives, 12a showed
higher affinity for the M3 receptor and almost the same
selectivity ratio between the M2 and M3 receptors, in
comparison with 12b, indicating that the relation-
ship between stereochemistry at the 1-position of the
3-thienyl derivatives (12a and 12b) and affinity for the
M3 receptor is similar to that for phenyl derivatives (9a
and 9b). All of the thienyl derivatives showed slightly
a Reagents and conditions: (a) 1 atm of H2, Raney Ni, 1 M aq
NaOH, rt; (b) MeOH, SOCl2, rt; (c) Ph3Bi, Cu(OAc)2, ClCH2CH2Cl,
80 °C; (d) (R)-34, NaH, toluene, reflux.
Results and Discussion
Affinities of the synthesized compounds for muscar-
inic receptor subtypes were measured based on inhibi-
tion of [3H]-pirenzepine binding to rat cortex (M1), [3H]-
quinuclidinyl benzilate binding to rat heart (M2), and
[3H]-N-methylscopolamine binding to rat salivary glands
(M3).24 These results are presented in Tables 1 and 2.
Initially, we focused our efforts on investigating the
conversion of the benzhydryl moiety in 8 to other ring
systems, including 1,2,3,4-tetrahydroisoquinoline (Table
1). Quinuclidin-3-yl 1-phenyl-1,2,3,4-tetrahydroisoquin-
oline-2-carboxylate (9), a mixture of the diastereomers
9a and 9b, showed high affinities for M1 and M3
receptors, and also showed a higher M3 selectivity over
the M2 receptor, compared with 8. On the other hand,
1-phenylisoindoline-2-carboxylate (10) and 1-phenyl-
1,2,3,4-tetrahydroquinoline-2-carboxylate (39) showed
poor affinities for the M3 receptor, compared to 9,
although 10 exhibited high selectivity for the M3 recep-
tor over the M2 receptor. The shift of the phenyl ring
from the 1- to the 4-position of the tetrahydroisoquino-
line ring (11) resulted in loss of affinity for the M3
receptor. These results indicate that the 1-phenyl-
1,2,3,4-tetrahydroisoquinoline ring is appropriate for
obtaining high affinity and selectivity for M3 receptors,
and 9a was therefore selected as a lead compound.
With respect to the 1-aryl-1,2,3,4-tetrahydroisoquino-
line-2-carboxylate derivatives (9a-9d, 12a-16d), the

6600 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21
Naito et al.
Table 1. Affinities of (R)-Quinuclidin-3-yl Carboxylate Derivatives (9-11 and 39) for Muscarinic Receptors
Ki (nM)a
compd
R1
R4
n
M1
M2
M3
selectivity: M2/M3
9b
Ph
Ph
H
H
1
0
1
1.4 (0.94-2.6)
8.4 (7.7-9.0)
52 (41-64)
9.4 (8.7-10)
1.5 (1.4-1.5)
5.9 (5.6-6.1)
28 (23-35)
440 (160-1300)
>1000
140 (99-190)
6.8 (6.3-7.4)
14 (12-16)
5.4 (4.7-6.3)
28 (26-30)
>1000
26 (24-27)
2.0 (1.7-2.3)
5.3 (5.2-5.4)
5.2
16
10c
11c
39c
8
H
Ph
s
5.4
3.4
2.6
1
a Values were estimated from 8 to 12 data points and the numbers in parentheses are 95% confidence limits. b A mixture of the
diastereomers 9a and 9b. c Compounds are mixtures of stereoisomers at the 1-position (10), the 4-position (11) and the 2-position (39).
Table 2. Affinities of Quinuclidin-3-yl 1-Substituted 1,2,3,4-Tetrahydroisoquinoline-2-carboxylate Derivatives (9a-d and 12a-16d)
for Muscarinic Receptors
Ki (nM)a
compd
R1
R4
config
M1
M2
M3
selectivity: M2/M3
9a
Ph
Ph
Ph
Ph
H
1R,3′R
1S,3′R
1R,3′S
1S,3′S
1S,3′R
1R,3′R
3′Rc
0.32 (0.27-0.36)
10 (6.0-18)
8.7 (7.6-9.8)
120 (100-130)
1600 (1400-1900)
3500 (2900-4100)
15 (13-17)
0.82 (0.77-0.87)
10 (9.1-11)
11
9b
H
12
9c
H
440 (400-480)
230 (160-350)
0.95 (0.70-1.3)
8.3 (5.7-12)
1.8 (1.3-2.7)
2.4 (0.51-12)
6.6 (5.4-8.1)
12 (5.8-24)
3.9 (1.3-12)
15 (8.4-27)
36 (27-45)
3.1 (2.4-3.8)
11 (6.5-16)
41 (17-65)
490 (430-540)
1300 (1100-1600)
3.5 (3.3-3.7)
21 (20-23)
3.3
2.7
4.3
5.2
3.6
5.2
3.3
0.6
3.0
>6.3
4.1
23
9d
H
12a
3-thienyl
3-thienyl
2-thienyl
2-thienyl
cHex
H
12b
H
110 (93-130)
13 (12-15)
13ab
13bb
14ab
14bb
15ad
15bd
16ab,e
16bb,e
16cb,f
16db,f
H
3.6 (2.3-5.5)
18 (17-19)
H
3′Rc
93 (82-110)
H
3′Rc
22 (18-27)
6.7 (6.1-7.3)
63 (55-72)
cHex
H
3′Rc
39 (32-48)
benzyl
benzyl
Ph
H
3′Rc
76 (58-100)
25 (22-28)
H
3′Rc
>1000
160 (89-280)
440 (370-510)
21 (18-24)
OH
OH
OH
OH
3′Rc
1800 (1600-2100)
480 (350-600)
1700 (1400-2100)
850 (690-1000)
Ph
3′Rc
Ph
1R,4R,3′R
1S,4S,3′R
150 (140-160)
35 (30-41)
11
24
Ph
a Values were estimated from 8 to 12 data points and the numbers in parentheses are 95% confidence limits. b Separated by preparative
HPLC (diastereomers eluted earlier: 13a, 14a, 16a and 16c, and later: 13b, 14b, 16b and 16d). c The configurations at 1- and 4-position
were not determined. d Compounds 15a and 15b were prepared from the 26‚hemi-(+)-DIBETA salt and 26‚hemi-(-)-DIBETA salt,
respectively. e Prepared from cis-1-phenyl-1,2,3,4-tetrahydroisoquinolin-4-ol (cis-29). f Prepared from trans-1-phenyl-1,2,3,4-tetrahydroiso-
quinolin-4-ol (trans-29).
higher affinities for the M1 receptor than those for the
M3 receptor. On the other hand, the low affinity and
selectivity for the M3 receptor of the 1-cyclohexyl deriva-
tives (14a and 14b) revealed that an aromatic substitu-
ent at the 1-position of the tetrahydroisoquinoline ring
is preferable. Moreover, the benzyl derivatives (15a and
15b) showed lower affinities for the M3 receptor than
9a and 9b, since the benzene ring of the benzyl group
is located too far from the basic nitrogen atom and can
rotate more freely than the benzene rings of 9a and 9b.
Furthermore, 14b, 15a, and 15b showed higher affini-
ties for the M1 receptor than for the M3 receptor,
suggesting differences of the environment around the
1-position of the 1,2,3,4-tetrahydroisoquinoline ring
between the M1 and M3 receptor. These results indicate
that benzene and thiophene rings adjacent to the
1-position of the 1,2,3,4-tetrahydroisoquinoline ring
adopt a conformation that is most appropriate for high
affinity and selectivity for the M3 receptor.
Last, a series of 4-hydroxyisoquinoline derivatives
(16a-d) were evaluated. Although 16b and 16d showed
moderate affinities for the M3 receptor, all 4-hydroxy-
isoquinoline derivatives had decreased affinities for the
M3 receptor, compared to 9a and 9b, indicating that
hydrophilic or hydrogen bond-donating character at the
4-position of the tetrahydroisoquinoline ring is unfavor-
able.
To understand the molecular features of the 1-phenyl-
1,2,3,4-tetrahydroisoquinoline-2-carboxylate derivatives
that lead to high affinity binding to the M3 receptor, a
molecular superimposition study was carried out. The
GASP program (Genetic Algorithm Similarity Pro-

Muscarinic Receptor Antagonists
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21 6601
Table 4. M3 Antagonistic Activities in Vivo
rhythmic contraction, salivary secretion, selectivity
compd
ED30 (mg/kg iv)a
ID50 (mg/kg iv)b
indexc
9a
9b
12a
12b
1
0.036 ( 0.013
0.18 ( 0.043
0.016 ( 0.0016
0.24 ( 0.12
0.20 ( 0.094
0.060 ( 0.025
0.058 ( 0.038
0.12 (0.089-0.14)
2.1 (1.9-2.3)
3.3
12
6.9
5.4
0.85
4.3
1.9
0.11 (0.093-0.13)
1.3 (1.0-1.9)
0.17 (0.13-0.21)
0.26 (0.23-1.8)
0.11 (0.092-0.013)
2
3
a Values are means ( SEM. b Values are means (95% confidence
limits). c Selectivity indices were calculated by dividing the IC50
values for salivary secretion by the ED30 values for bladder
contraction.
Figure 2. Superimposition of 7 (green), 8 (yellow) and 9a
(gray). All hydrogen atoms are hidden to improve visualization.
Table 3. Distances between the Centroids of the Benzene
Rings, the Nitrogen Atoms of the Quinuclidine Rings and the
Carbonyl Oxygen Atoms of the Carbamate Groups, and the
Calculated Energy in the Superimposition Study of 7, 8 and 9a
Table 5. Comparison of Compounds 1 and 9b
M3 antagonism
M1
M2
rhythmic
contraction
salivary
secretion
ID50
antagonism: antagonism:
pressor
ID50
bradycardia
DR10
ED30
compd (mg/kg iv)a
(mg/kg iv)b
(mg/kg iv)b
(mg/kg iv)b
9b
1
0.18 ( 0.043 2.1 (1.9-2.3)
0.20 ( 0.094 0.17 (0.13-0.21) 1.1 (0.61-1.8) 1.6 (1.1-2.0)
2.8 (2.6-3.0) 4.2 (3.0-7.5)
a Values are means ( SEM. b Values are means (95% confidence
limits).
7
8
9a
restriction of the benzhydrylcarbamate moiety in 8
through formation of a 1-phenyl-1,2,3,4-tetrahydroiso-
quinoline-2-carboxylate, may increase selectivity for the
M3 receptor over the M2 receptor.
a (centroid 1 - basic nitrogen)
b (centroid 2 - basic nitrogen)
c (centroid 1 - centroid 2)
6.2
8.4
6.3
8.9
6.6
8.9
4.3
4.7
4.7
d (centroid 1 - carbonyl oxygen)
e (basic nitrogen - carbonyl oxygen)
f (centroid 2 - carbonyl oxygen)
energy (kcal/mol)
3.2
3.3
3.5
4.8
4.4
4.4
Among the compounds exhibiting high affinity and
selectivity for the M3 receptor, 9a, 9b, 12a, and 12b
were selected for evaluation in vivo, in tests examining
reflexly evoked rhythmic contraction and oxotremorine-
induced salivary secretion in rats. Three reference
compounds, nonselective oxybutynin (1) and bladder-
selective tolterodine (2) and darifenacin (3), were also
evaluated. As shown in Table 4, all compounds showed
potent inhibitory activities on bladder pressure in a
reflexly evoked rhythmic contraction test, with 9a and
12a showing particularly higher inhibitory activities
with some bladder selectivity, compared to 1. On the
other hand, 9b and 12b showed almost the same
inhibitory activities on bladder pressure, compared to
1, and less potent inhibitory activities on salivary
secretion. Among these compounds, 9b showed more
than 10-fold selective inhibitory activity on bladder
pressure versus salivary secretion. The order of bladder
selectivity in rats was 9b > 2, 12a, 12b > 3, 9a > 1.
Bladder selectivity of 9b was also observed in vitro.26
Compound 9b was selected for further pharmacologi-
cal evaluation, since it showed the highest selectivity
for bladder contraction versus salivary secretion. The
results are shown in Table 5. In comparison with 1, 9b
showed less potent activity against agonist-induced
pressor and bradycardia in pithed rat, suggesting that
9b is a weaker M1 and M2 receptor antagonist, respec-
tively. On the basis of these results, 9b could potentially
be a bladder-selective M3 antagonist with few side
effects.
3.7
5.6
5.7
17.98
17.97
14.52
14.52
15.69
15.65
minimum energy (kcal/mol)
gram)25 was used to superimpose the most potent
diastereomer among the quinuclidin-3-yl 1-phenyl-
1,2,3,4-tetrahydroisoquinoline-2-carboxylates, 9a, and
compounds 7 and 8 (the R isomer was used in this
study). GASP does not require prior knowledge concern-
ing either the receptor or the pharmacophore pattern,
and it performs automatic molecular alignment with full
conformational flexibility of the ligands. The results are
shown in Figure 2 and Table 3. In this model, the basic
nitrogen atoms and the centroids of the benzene rings
in 7, 8, and 9a overlapped well. Taking into consider-
ation that even the less potent diastereomer (9b) showed
relatively high affinity for the M3 receptor, with a Ki
value of 10 nM, the benzene ring of the tetrahydroiso-
quinoline moiety (benzene ring 1) may be more impor-
tant for binding to the M3 receptor than the benzene
ring at the 1-position of the tetrahydroisoquinoline ring
(benzene ring 2) and the benzene ring at the 1-position
may modulate the interaction with the receptor. Fur-
thermore, the remarkably decreased affinity for M3
receptor of benzyl derivatives (15a and 15b) suggests
that the benzene ring 2 in 9a may be fixed for preferred
interaction with the M3 receptor. On the other hand,
significant overlap of the carbonyl oxygen atoms of the
three compounds was not observed in the selected model
or in other models. This suggests that the carbamate
junction is necessary for locking the molecular confor-
mation between the hydrophobic region and the amine
ring, to generate a conformation that is suitable for
interaction with the M3 receptor. Consequently, proper
arrangement of the two benzene rings and the nitrogen
atom in the basic ring, achieved by conformational
Conclusion
In the course of our continuing efforts to develop
potent and bladder-selective M3 antagonists, we de-
signed and synthesized a series of quinuclidin-3-yl
1-aryl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate de-

6602 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21
Naito et al.
next step without further purification. To the ice-cooled
solution of 1-(3-thienyl)-3,4-dihydroisoquinoline (41.7 g) in
ethanol (400 mL) was portionwisely added sodium borohydride
(14.8 g, 412 mmol). The mixture was stirred at room temper-
ature for 2.5 days and then poured into ice-water. The
resulting solid was collected, washed with water, and dried
at 30 °C in vacuo to give 1-(3-thienyl)-1,2,3,4-tetrahydroiso-
quinoline (23) (34.4 g, 82%) as a pale brown solid: 1H NMR
(CDCl3) δ 1.87 (1H, br s), 2.75-2.90 (1H, m), 2.90-3.00 (1H,
m), 3.00-3.15 (1H, m), 3.15-3.25 (1H, m), 5.22 (1H, s), 6.88
(1H, d, J ) 8.0 Hz), 7.00 (1H, dd, J ) 4.8, 1.6 Hz), 7.00-7.30
(5H, m); EI-MS m/z 215 (M+).
rivatives and related compounds, as conformationally
restricted analogues of quinuclidin-3-yl benzhydrylcar-
bamate (8). Binding assays showed that the quinuclidin-
3-yl 1-aryl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate
derivatives had higher selectivities for the M3 receptor
over the M2 receptor, compared to 8, and had high
affinities for the M3 receptor. Among these derivatives,
(+)-(1S,3’R)-quinuclidin-3’-yl 1-phenyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate monohydrochloride (9b) ex-
hibited almost the same inhibitory effect on bladder
contraction and about a 10 times less potent inhibitory
effect on salivary secretion in rats, in comparison with
1, indicating that conformational restriction of the
benzhydrylcarbamate moiety in 8 by formation of a
1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate can
lead to an increase in subtype selectivity and bladder
selectivity. Compound 9b was selected as a clinical
candidate in the form of its monosuccinate salt, solif-
enacin succinate (YM905),26-28 and it has recently been
Resolution of 1-Substituted 1,2,3,4-Tetrahydroiso-
quinoline Derivatives. (+)-(S)-1-Phenyl-1,2,3,4-tetra-
hydroisoquinoline [(+)-22]. Resolution of 1-phenyl-1,2,3,4-
tetrahydroisoquinoline (22) was carried out as the reported
method14 with minor modification. Racemic 22 (1.88 kg, 8.97
mol) was converted to the corresponding (-)-tartrate in ethanol
(16 L) followed by recrystallization from water (6 L) to give
the (-)-tartrate (1.35 kg, 42%) as colorless crystals: mp 187-
189 °C; 1H NMR (DMSO-d6) δ: 2.90-3.00 (1H, m), 3.10-3.20
(1H, m), 3.20-3.25 (1H, m), 3.30-3.35 (1H, m), 4.03 (2H, s),
5.49 (1H, s), 6.69 (1H, d, J ) 7.9 Hz), 7.11 (1H, t, J ) 6.1 Hz),
7.20-7.25 (2H, m), 7.30-7.45 (5H, m). FAB-MS m/z 210
(MH+). The (-)-tartrate (1.35 kg) was neutralized with aque-
ous NaOH solution, then extracted with ethyl acetate. The
organic layer was washed with water, then brine, and con-
centrated in vacuo. The resulting crystals were recrystallized
from hexane to give (+)-22 (627 g, 80%) as colorless crystals:
1
mp 80-82 °C; H NMR (CDCl3) δ 1.77 (1H, br s), 2.80-2.90
(1H, m), 3.00-3.15 (2H, m), 3.20-3.30 (1H, m), 5.10 (1H, s),
6.75 (1H, d, J ) 7.3 Hz), 7.03 (1H, m), 7.14 (2H, d, J ) 3.7
Hz), 7.25-7.35 (5H, m); EI-MS m/z 209 (M+); [R]25D ) +47.6°
(c ) 2.83, CCl4).
approved by the United States Food and Drug Admin-
istration for the treatment of overactive bladder with
symptoms of urgency, frequency, and urge incontinence.
(-)-(R)-1-Phenyl-1,2,3,4-tetrahydroisoquinoline [(-)-
22]: mp 80-82 °C; [R]25D ) -47.8° (c ) 2.88, CCl4) [lit.14 [R]25
D
Experimental Section
) -47.6° (c ) 6.46, CCl4)]. 1H NMR and MS spectra are similar
to those of (+)-(S)-22.
General. Melting points were determined using a Yanaco
micro melting apparatus and are uncorrected. Proton nuclear
magnetic resonance (1H NMR) spectra were obtained in CDCl3
or dimethyl sulfoxide-d6 (DMSO-d6) with a JNM-EX400, JNM-
GX500 or JNM-A500 spectrometer. Chemical shifts are re-
corded in parts per million (δ), downfield relative to tetra-
methylsilane as an internal standard with coupling constants
(J) reported in hertz (Hz). The peak shapes are denoted as
follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet;
br, broad. Mass spectra (MS) were recorded on a JEOL JMS-
DX300 or a Hitachi M-80 mass spectrometer. Elementary
analyses were carried out on a Yanaco MT-3 or a Yanaco MT-5
CHN analyzer and a Yokogawa IC 7000S Ion Chromato-
analyzer. Optical rotations were measured on a Horiba SEPA-
200 polarimeter. X-ray diffraction measurements were made
with a Rigaku AFC5R diffractometer using Cu KR radiation.
Chromatographic separations were performed on a silica gel
column using Wakogel C-200 or Merck Silica gel 60 (0.040-
0.063 mm). Analytical thin-layer chromatography (TLC) was
carried out on glass plates precoated with Merck silica gel 60
(+)-1-(3-Thienyl)-1,2,3,4-tetrahydroisoquinoline [(+)-
(23)]. Racemic 23 (31.69 g, 0.15 mol) was converted to the
corresponding (-)-mandelate in ethanol-water (20:1) followed
by recrystallization from ethanol-water (20:1) twice to give
the (-)-mandelate (14.62 g, 25%) as colorless crystals: mp
1
132-133 °C; H NMR (DMSO-d6) δ 2.75-3.20 (4H, m), 4.80
(1H, s), 5.37 (1H, s), 6.80 (1H, d, J ) 7.6 Hz), 7.02 (1H, dd, J
) 5.2, 1.2 Hz), 7.15-7.40 (10H, m), 7.50 (1H, dd, J ) 4.8, 2.8
Hz); FAB-MS m/z 216 (MH+). The (-)-mandelate (14.42 g, 39
mmol) was neutralized with aqueous NaOH solution, then
extracted with ethyl acetate. The organic layer was washed
with water and then brine and concentrated in vacuo. The
resulting crystals (8.37 g) were recrystallized from hexane (160
mL) to give (+)-23 (6.83 g, 81%) as colorless crystals: mp 100-
1
101 °C; H NMR (CDCl3) δ 1.76 (1H, br s), 2.83 (1H, dt, J )
16, 5.6 Hz), 2.90-3.00 (1H, m), 3.08 (1H, ddd, J ) 12, 7.2, 5.6
Hz), 3.22 (1H, dt, J ) 12, 6.0 Hz), 5.23 (1H, s), 6.88 (1H, d, J
) 7.6 Hz), 7.00 (1H, dd, J ) 4.8, 0.8 Hz), 7.05-7.15 (4H, m),
7.27 (1H, dd, J ) 4.8, 2.8 Hz); EI-MS m/z 215 (M+); [R]25
+10.7° (c ) 2.00, CCl4).
)
D
F254
.
(-)-1-(3-Thienyl)-1,2,3,4-tetrahydroisoquinoline [(-)-
23]: mp 100-101 °C; [R]25D ) -9.95° (c ) 2.00, CCl4). 1H NMR
and MS spectra are similar to those of (+)-23.
Authentic Material. Oxybutynin hydrochloride (1) was
purchased from Sigma Co. Tolterodine tartrate (2) and darifena-
cin (3) were prepared at Yamanouchi Pharmaceutical Co., Ltd.
General Method for the Synthesis of 1-Substituted
1,2,3,4-Tetrahydoroisoquinolines. 1-(3-Thienyl)-1,2,3,4-
tetrahydroisoquinoline (23). N-(2-Phenylethyl)thiophene-
3-carboxamide29 (18, 49.9 g, 234 mmol) was dissolved in xylene
(500 mL) at 70 °C. To the solution were added phosphorus
pentoxide (61.2 g, 431 mmol) and phosphoryl chloride (174 mL,
1.87 mol) and refluxed for 2.5 h. After the mixture was cooled
to 30 °C, the solution was removed by decantation and washed
with toluene. The residue was quenched with water and 20%
aqueous NaOH solution and then extracted with ethyl acetate.
The organic layer was washed with water, dried over MgSO4,
and evaporated in vacuo to give 1-(3-thienyl)-3,4-dihydroiso-
quinoline (41.7 g) as a dark brown oil, which was used for the
1-Benzyl-1,2,3,4-tetrahydroisoquinoline
Hemi-(+)-
DIBETA Salt [26 Hemi-(+)-DIBETA Salt]. Racemic 2613
(27.6 g, 123 mmol) was converted to the corresponding hemi-
(+)-DIBETA salt in ethanol followed by recrystallization from
ethanol-water (20:1) three times to give the hemi-(+)-DIBETA
salt (7.03 g, 10%) as colorless crystals: 1H NMR (DMSO-d6) δ
2.72-2.93 (2H, m), 2.94-3.70 (2H, m), 3.17-3.30 (2H, m), 4.43
(1H, dd, J ) 8.4, 5.3 Hz), 5.63 (1H, s), 7.10-7.35 (9H, m), 7.47
(2H, t, J ) 7.5 Hz), 7.61 (1H, t, J ) 7.5 Hz), 7.88-7.95 (2H,
m); FAB-MS m/z 224 (MH+). The optical purity was deter-
mined after neutralization as >99% by chiral HPLC [Chiral-
pak AD (4.6 × 250 mm; Daicel Chem. Co.), eluent: hexane-
2-propanol-diethylamine (80:20:0.1)].

Muscarinic Receptor Antagonists
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21 6603
1-Benzyl-1,2,3,4-tetrahydroisoquinoline
Hemi-(-)-
2.10-2.40 (1H, m), 2.70-3.00 (2H, m), 3.00-3.30 (5H, m),
3.30-3.70 (2H, m), 3.85-4.00 (1H, m), 4.85-5.05 (1H, m), 6.28
(1H, s), 7.10-7.45 (9H, m), 10.87 (1H, br s); FAB-MS m/z 363
(MH+); Anal. (C23H26N2O2‚HCl) C, H, N, Cl.
(3′R,4RS)-Quinuclidin-3′-yl 4-Phenyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate (11): obtained in 25% yield from
4-phenyl-1,2,3,4-tetrahydroisoquinoline (28)13 and (R)-34 as a
yellow oil in 25% yield; 1H NMR (DMSO-d6) δ 1.10-1.35 (1H,
m), 1.35-1.75 (3H, m). 1.80-2.10 (2H, m), 2.60-3.00 (5H, m),
3.10-3.30 (1H, m), 3.60-3.85 (1H, m), 3.90-4.10 (1H, m),
4.15-4.25 (1H, m), 4.45-4.80 (2H, m), 6.90-7.35 (9H, m);
FAB-MS m/z 363 (MH+); Anal. (C23H26N2O2‚0.3H2O) C, H, N.
(+)-(1R,3′R)-Quinuclidin-3′-yl 1-(3-Thienyl)-1,2,3,4-tetra-
hydroisoquinoline-2-carboxylate Monooxalate (12b): ob-
tained in 33% yield from (+)-23 and (R)-34 as colorless crystals,
mp 166-167 °C (aq. ethanol); [R]25D ) +57.6° (c ) 1.00, H2O);
1H NMR (DMSO-d6) δ 1.60-2.10 (4H, m), 2.20-2.35 (1H, m),
2.75-3.45 (8H, m), 3.50-3.70 (1H, m), 3.80-3.95 (1H, m),
4.85-5.00 (1H, m), 6.27 (1H, s), 6.90-7.10 (1H, m), 7.15-7.30
(5H, m), 7.49 (1H, dd, J ) 4.4, 3.2 Hz).; FAB-MS m/z 369
(MH+). Anal. (C21H24N2O2S‚C2H2O4) C, H, N, S.
DIBETA Salt [26 Hemi-(-)-DIBETA Salt]: obtained in 10%
yield as colorless crystals from the mother liquor of 26 hemi-
(+)-DIBETA salt. The optical purity was determined after
neutralization as >99% by chiral HPLC.
(+)-(1S,3′R)-Quinuclidin-3′-yl 1-Phenyl-1,2,3,4-tetra-
hydroisoquinoline-2-carboxylate Monohydrochloride
(9b). Method A. To a suspension of (+)-22 (5.34 g, 26 mmol)
and potassium carbonate (5.28 g, 38 mmol) in dichloromethane
(100 mL) cooled in an ice bath was added ethyl chloroformate
(2.91 mL, 27 mmol) in dichloromethane (10 mL), and the
mixture was stirred at room temperature overnight. To the
mixture was added water, and the mixture was stirred at room
temperature for 30 min. The organic layer was separated,
washed with water and brine, dried over MgSO4, and concen-
trated in vacuo. The residue was purified by column chroma-
tography on silica gel using hexanes-ethyl acetate (10:1) as
an eluent to give (+)-30 (7.20 g, 100%) as a colorless oil: [R]25
D
1
) +199° (c ) 1.03, EtOH); H NMR (DMSO-d6) δ 1.20-1.50
(3H, m), 2.70-2.80 (1H, m), 2.90-3.10 (1H, m), 3.20-3.30 (1H,
m), 3.90-4.35 (3H, m), 6.20-6.55 (1H, m), 6.95-7.20 (9H, m);
FAB-MS m/z 282 (MH+). To a solution of (+)-30 (12.0 g, 43
mmol) and (+)-(R)-quinuclidin-3-ol [(R)-34, 16.3 g, 128 mmol]
in toluene (120 mL) was added sodium hydride (1.69 g, 42
mmol), and the mixture was heated at 140 °C (oil bath
temperature) for 3 h with removal of resulting ethanol. The
mixture was cooled to room temperature, poured into brine,
then extracted with ethyl acetate. The organic layer was
washed with water and then extracted with 20% hydrochloric
acid. The aqueous layer was alkalized with 1 M aqueous NaOH
solution to pH 9-10 and extracted with ethyl acetate. The
organic layer was washed with brine, dried over MgSO4,
and concentrated in vacuo to give (1S,3′R)-quinuclidin-3′-yl
1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate (13.9 g,
89%) as a colorless oil. The free base was converted to the
corresponding hydrochloride salt and recrystallized from
acetonitrile-diethyl ether to give (+)-(1S,3′R)-quinuclidin-3′-
yl 1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate mono-
hydrochloride (9b, 10.1 g, 66%) as colorless crystals: mp 212-
214 °C; [R]25D ) +102° (c ) 1.00, EtOH); 1H NMR (DMSO-d6)
δ 1.70-2.10 (4H, m), 2.20-2.35 (1H, m), 2.75-3.65 (9H, m),
3.80-3.95 (1H, m), 4.85-5.00 (1H, m), 6.28 (1H, s), 7.10-7.40
(9H, m), 10.83 (1H, br s); FAB-MS m/z 363 (MH+); Anal.
(C23H26N2O2‚HCl) C, H, N, Cl.
(-)-(1S,3′R)-Quinuclidin-3′-yl 1-(3-Thienyl)-1,2,3,4-tetra-
hydroisoquinoline-2-carboxylate Mono-(-)-tartrate (12a).
Method B. To a solution of (-)-1-(3-thienyl)-1,2,3,4-tetrahydro-
isoquinoline [(-)-23, 3.23 g, 15 mmol] in pyridine (45 mL) at
-20 °C was added (R)-quinuclidin-3-yl chloroformate mono-
hydrochloride (35,21 3.39 g, 15 mmol), and the mixture was
stirred at room temperature for 1.5 h. After 35 (0.34 g, 1.5
mmol) was added, the mixture was stirred at room tempera-
ture for additional 30 min. The resulting mixture was diluted
with ethyl acetate and extracted with water and then 1%
hydrochloric acid. The combined aqueous layer was washed
with ethyl acetate, alkalized with 1 M aqueous NaOH solution
to pH 10, and extracted with ethyl acetate. The organic layer
was washed with water, dried over MgSO4, and concentrated
in vacuo. The residue was chromatographed on silica gel with
chloroform-methanol-28% ammonium hydroxide solution (50:
1:0.1) as an eluent to give (-)-(1S,3′R)-quinuclidin-3′-yl 1-(3-
thienyl)-1,2,3,4-tetrahydroisoquinoline-2-carboxylate (3.66 g,
66%) as a yellow oil. The free base (0.57 g, 1.5 mmol) was
converted to the corresponding mono-(-)-tartrate and recrys-
tallized from ethanol-water to give 12a (0.43 g, 61%) as
colorless crystals: mp 176-178 °C; [R]25 ) -104° (c ) 1.01,
D
H2O); 1H NMR (DMSO-d6) δ 1.80-2.00 (4H, m), 2.70-3.15 (7H,
m), 3.30-3.50 (2H, m), 3.80-4.00 (1H, m), 4.02 (2H, s), 4.80-
4.90 (1H, m), 6.28 (1H, s), 6.90-7.30 (6H, m), 7.49 (1H, dd, J
) 5.4, 2.9 Hz); FAB-MS m/z 369 (MH+); Anal. (C21H24N2O2S‚
C4H4O4) C, H, N, S.
(1RS,3′R)-Quinuclidin-3′-yl 1-Phenyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate (9): obtained from racemic
1-phenyl-1,2,3,4-tetrahydroisoquinoline (22) and (R)-34 as a
yellow oil in 33% yield; 1H NMR (DMSO-d6) δ 1.10-2.00 (5H,
m), 2.20-2.95 (7H, m), 2.95-3.15 (1H, m), 3.20-3.55 (1H, m),
3.80-3.95 (1H, m), 4.55-4.70 (1H, m), 6.24 (1H, s), 7.00-7.40
(9H, m); FAB-MS m/z 363 (MH+); Anal. (C23H26N2O2) C, H, N.
(1R,3′R)-Quinuclidin-3′-yl 1-Phenyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate Monohydrochloride (9a): ob-
tained in 32% yield from (-)-22 and (R)-34 as colorless crystals,
mp 197-199 °C (acetonitrile-diethyl ether); [R]25D ) -151° (c
) 0.500, EtOH); 1H NMR (DMSO-d6) δ 1.55-2.10 (4H, m),
2.10-2.40 (1H, m), 2.70-2.95 (2H, m), 3.00-3.70 (7H, m),
3.85-4.00 (1H, m), 4.85-5.00 (1H, m), 6.27 (1H, s), 7.10-7.40
(9H, m), 10.80 (1H, br s); FAB-MS m/z 363 (MH+); Anal.
(C23H26N2O2‚HCl) C, H, N, Cl.
(1R,3′S)-Quinuclidin-3′-yl 1-Phenyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate Monohydrochloride (9c): ob-
tained in 40% yield from (-)-22 and (S)-34 as colorless crystals,
mp 212-214 °C (acetonitrile-diethyl ether); [R]25D ) -97.4° (c
) 0.500, EtOH); 1H NMR (DMSO-d6) δ 1.70-2.10 (4H, m),
2.20-2.35 (1H, m), 2.75-3.70 (9H, m), 3.80-3.95 (1H, m),
4.85-5.00 (1H, m), 6.28 (1H, s), 7.10-7.40 (9H, m), 11.01 (1H,
br s); FAB-MS m/z 363 (MH+); Anal. (C23H26N2O2‚HCl) C, H,
N, Cl.
(1S,3′S)-Quinuclidin-3′-yl 1-Phenyl-1,2,3,4-tetrahydroiso-
quinoline-2-carboxylate Monohydrochloride (9d): ob-
tained in 74% yield from (+)-22 and (S)-34 as colorless crystals,
mp 194-195 °C (acetonitrile-diethyl ether); [R]25D ) +163° (c
) 0.500, EtOH); 1H NMR (DMSO-d6) δ 1.50-2.05 (4H, m),
(1RS,3′R)-Quinuclidin-3′-yl 1-Phenylisoindoline-2-car-
boxylate (10): prepared from 1-phenylisoindoline (27)19 and
1
35 as pale yellow amorphous in 60% yield; H NMR (DMSO-
d6) δ 1.80-2.10 (4H, m), 2.30-2.40 (1H, m), 2.75-3.60 (6H,
m), 3.90-4.05 (1H, m), 6.05-6.20 and 6.30-6.50 (total 1H, m),
7.05-7.35 (9H, m); FAB-MS m/z 349 (MH+); Anal. (C22H24N2O2‚
0.3H2O) C, H, N.
(-)-(3′R)-Quinuclidin-3′-yl 1-Benzyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate Monohydrochloride (15a):
prepared from 1-benzyl-1,2,3,4-tetrahydroisoquinoline hemi-
(+)-DIBETA salt [26‚hemi-(+)-DIBETA salt] and 35 as color-
less crystals in 44% yield, mp 248-250 °C (ethanol-aceto-
1
nitrile-diethyl ether); [R]25 ) -79.0° (c ) 0.500, EtOH); H
D
NMR (DMSO-d6) δ 1.40-2.05 (5H, m), 2.65-2.90 (2H, m),
2.95-3.20 (7H, m), 3.35-3.55 (2H, m), 3.85-4.10 (1H, m),
4.35-4.45, 4.70-4.80 (total 1H, m), 5.28 (1H, t, J ) 7.2 Hz),
7.10-7.40 (9H, m), 10.40 (1H, br s); FAB-MS m/z 377 (MH+);
Anal. (C24H28N2O2‚HCl) C, H, N, Cl.
(+)-(3′R)-Quinuclidin-3′-yl 1-Benzyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate Monohydrochloride (15b):
prepared in 57% yield from 26 hemi-(-)-DIBETA salt and 35
as colorless crystals, mp 132-134 °C (ethanol-diethyl ether);
[R]25D ) +54.0° (c ) 0.507, EtOH); 1H NMR (DMSO-d6) δ 1.50-
2.10 (5H, m), 2.75-3.25 (7H, m), 3.30-3.55 (2H, m), 3.70-
4.00 (1H, m), 4.05-4.15 (1H, m), 4.55-4.75 (1H, m), 5.15-

6604 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21
Naito et al.
5.35 (1H, m), 7.10-7.40 (9H, m), 10.44 (1H, br s); FAB-MS
m/z 377 (MH+); Anal. (C24H28N2O2‚HCl‚0.75H2O) C, H, N, Cl.
6.1 Hz), 6.25 (1H, s), 7.10-7.35 (8H, m), 7.44 (1H, d, J ) 7.3
Hz); FAB-MS m/z 379 (MH+); Anal. (C23H26N2O3‚0.2H2O) C,
H, N.
Separation of Diastereomers. Compounds 13a, 13b, 14a,
14b, 16a-d were obtained as yellow oils by preparative HPLC
separation (Chiralpak AD, 20 × 250 mm; Daicel Chem. Co.)
with hexane-2-propanol-diethylamine (80:20:0.1 or 60:40:0.1)
as eluents (the former eluted diastereomers: 13a, 14a, 16a,
16c, and the latters: 13b, 14b, 16b, and 16d).
(3′R)-Quinuclidin-3′-yl 1-(2-Thienyl)-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate (13a and 13b). A mixture of
13a and 13b was prepared from 1-(2-thienyl)-1,2,3,4-tetra-
hydroisoquinoline (24)13 in 64% yield by Method A.
13a: a yellow oil; [R]25D ) -135° (c ) 1.00, EtOH); 1H NMR
(DMSO-d6) δ 1.35-2.25 (6H, m), 2.70-3.10 (6H, m), 3.20-3.45
(2H, m), 3.90-4.30 (1H, m), 4.80-4.90 (1H, m), 6.40-6.65 (1H,
m), 6.65-6.80 (1H, m), 6.88 (1H, dd, J ) 4.8, 3.2 Hz), 7.15-
7.30 (5H, m); FAB-MS m/z 369 (MH+); Anal. (C21H24N2O2S‚
0.2H2O) C, H, N, S.
13b: a yellow oil; [R]25D ) +118° (c ) 1.00, EtOH); 1H NMR
(DMSO-d6) δ 1.35-2.10 (6H, m), 2.65-3.10 (6H, m), 3.20-3.45
(2H, m), 3.90-4.50 (1H, m), 4.75-4.85 (1H, m), 6.40-6.80 (2H,
m), 6.88 (1H, dd, J ) 4.8, 3.2 Hz), 7.15-7.30 (7H, m); FAB-
MS m/z 369 (MH+); Anal. (C21H24N2O2S‚0.2H2O) C, H, N, S.
(3′R)-Quinuclidin-3′-yl 1-Cyclohexyl-1,2,3,4-tetrahydro-
isoquinoline-2-carboxylate (14a and 14b). A mixture of
14a and 14b was prepared from 1-cyclohexyl-1,2,3,4-tetra-
hydroisoquinoline (25)13 in 99% yield by Method B.
14a: a yellow oil; [R]25D ) -10.0° (c ) 1.00, EtOH); 1H NMR
(CDCl3) δ 1.00-1.30 (5H, m), 1.30-2.15 (12H, m), 2.60-3.05
(6H, m), 3.15-4.09 (3H, m), 4.70-4.90 (2H, m), 7.06-7.25 (4H,
m); EI-MS m/z 368 (M+); Anal. (C23H32N2O2‚0.25H2O) C, H,
N.
14b: a yellow oil; [R]25D ) +7.29° (c ) 1.00, EtOH); 1H NMR
(CDCl3) δ 1.00-1.30 (5H, m), 1.35-2.10 (12H, m), 2.65-3.05
(6H, m), 3.15-4.07 (3H, m), 4.67-4.88 (2H, m), 7.05-7.22 (4H,
m); EI-MS m/z 368 (M+); Anal. (C23H32N2O2‚0.25H2O) C, H,
N.
Methyl 1,2,3,4-Tetrahydroquinoline-2-carboxylate (37).
Quinaldic acid (36, 5.07 g, 29 mmol) was hydrogenated at room
temperature overnight in the presence of Raney Ni in 1 M
aqueous NaOH solution (100 mL). After the catalyst was
removed by filtration, the filtrate was neutralized with con-
centrated HCl (8.5 mL) and concentrated in vacuo. The
resulting residue was dissolved in methanol (75 mL), and the
solution was cooled in an ice bath. To the solution was
cautiously added thionyl chloride (8.5 mL), and the mixture
was stirred at room temperature overnight. After the mixture
was concentrated in vacuo, the residue was diluted with water,
alkalized with potassium carbonate, and then extracted with
ethyl acetate. The organic layer was washed with water, dried
over MgSO4, and then evaporated in vacuo. The residue was
chromatographed on silica gel with hexanes-ethyl acetate (5:
1) as an eluent to give 37 (4.12 g, 74%) as a pale yellow oil:
1H NMR (CDCl3) δ 1.95-2.05 (1H, m), 2.20-2.35 (1H, m),
2.70-2.90 (2H, m), 3.77 (3H, s), 4.03 (1H, dd, J ) 8.8, 3.9 Hz),
4.35 (1H, br s), 6.58 (1H, d, J ) 7.3 Hz), 6.64 (1H, dd, J ) 8.8,
7.3 Hz), 6.90-7.05 (2H, m); EI-MS m/z 191 (M+).
Methyl 1-Phenyl-1,2,3,4-tetrahydroquinoline-2-car-
boxylate (38). A mixture of 37 (2.00 g, 10 mmol), triphenyl-
bismuthine (5.53 g, 12 mmol), and copper(II) acetate (1.90 g,
10 mmol) in 1,2-dichloroethane (35 mL) was stirred at 80 °C
for 5 days. After the insoluble material was filtered off, the
filtrate was concentrated in vacuo. The residue was chromato-
graphed on silica gel with hexanes-ethyl acetate (10:1) as an
eluent to give 38 (0.23 g, 9%) as a brown oil: 1H NMR (CDCl3)
δ 2.00-2.40 (2H, m), 2.65-2.90 (2H, m), 3.65 (3H, s), 4.48 (1H,
t, J ) 4.4 Hz), 6.50-6.80 (2H, m), 6.80-7.50 (10H, m); FAB-
MS m/z 267 (M+).
(2RS,3′R)-Quinuclidin-3′-yl 1-Phenyl-1,2,3,4-tetrahydro-
quinoline-2-carboxylate (39): prepared from methyl
1-phenyl-1,2,3,4-tetrahydroquinoline-2-carboxylate (38) in 43%
yield in the same manner to Method A as a yellow amor-
phous: 1H NMR (CDCl3) δ 1.20-1.35 (1H, m), 1.40-1.70 (3H,
m), 1.85-2.00 (1H, m), 2.20-2.90 (9H, m), 3.10-3.15 (1H, m),
4.52 (1H, ddd, J ) 9.2, 5.6, 3.6 Hz), 4.80-4.85 (1H, m), 6.60-
6.80 (2H, m), 6.90-7.40 (7H, m); EIMS m/z 362 (M+); Anal.
(C23H26N2O2‚0.25H2O) C, H, N.
cis-(3′R)-Quinuclidin-3′-yl 4-Hydroxy-1-phenyl-1,2,3,4-
tetrahydroisoquinoline-2-carboxylate (16a and 16b). A
mixture of 16a and 16b was prepared from cis-1-phenyl-
1,2,3,4-tetrahydroisoquinoline-4-ol (cis-29)20 in 72% yield by
Method B.
X-ray Crystallographic Analysis. The configurations of
compounds 9b, 12b, 16c, and 16d were determined by X-ray
crystallographic analysis.
16a: a colorless amorphous; [R]25 ) -196° (c ) 0.500,
D
EtOH); 1H NMR (DMSO-d6, 90 °C) δ 1.20-1.70 (4H, m), 1.90-
2.00 (1H, m), 2.50-2.80 (4H, m), 2.85-3.15 (3H, m), 4.16 (1H,
dd, J ) 13, 6.1 Hz), 4.55-4.70 (2H, m), 5.49 (1H, d, J ) 6.1
Hz), 6.21 (1H, s), 6.97 (1H, J ) 7.3 Hz), 7.00-7.40 (7H, m),
7.62 (1H, J ) 7.3 Hz); FAB-MS m/z 379 (MH+); Anal.
(C23H26N2O3‚0.5H2O) C, H, N.
Compound 9b was converted to the hydrogen bromide salt
(9e) and crystallized from ethanol-diethyl ether for X-ray
crystallographic analysis. The absolute configuration is 1S,3′R
by the comparison of intensities of Bijvoet’s pairs. Formula,
C23H27N2O2Br; crystal system, monoclinic; space group, P21;
lattice parameters, a ) 7.550 (3) Å, b ) 33.392 (3) Å, c ) 9.425
(2) Å, â ) 91.28 (2) °, V ) 2375.6 (10) Å3; Dcalc, 1.34 g/cm3; Z
value, 4.0; F000, 1004; final R value, R ) 0.061, RW ) 0.103;
goodness of fit indicator, 1.30; Flack parameter ) -0.03 (2).
Compound 12b was converted to the phosphate salt (12c)
and recrystallized from ethanol-diethyl ether for X-ray crys-
tallographic analysis. The absolute configuration of 12b is R
by the comparison of intensities of Bijvoet’s pairs. Formula,
C21H27N2O6PS; crystal system, monoclinic; space group, P21;
lattice parameters, a ) 21.570 (1) Å, b ) 6.6041 (7) Å, c )
7.971 (1) Å, â ) 94.771 (9) °, V ) 1131.6 (2) Å3; Dcalc, 1.37 g/cm3;
Z value, 2.0; F000, 2522; final R value, R ) 0.047, RW ) 0.070;
goodness of fit indicator, 1.26; Flack parameter ) -0.004(30).
16c: Formula, C23H26N2O3; crystal system, orthorhombic;
space group, P212121; lattice parameters, a ) 9.945 (2) Å, b )
31.993 (1) Å, c ) 6.274 (1) Å, V ) 1996.3 (6) Å3; Dcalc, 1.26
16b: a colorless amorphous; [R]25 ) +197° (c ) 0.500,
D
EtOH); 1H NMR (DMSO-d6, 90 °C) δ 1.25-1.80 (4H, m), 1.90-
2.00 (1H, m), 2.50-2.80 (5H, m), 2.90-3.15 (2H, m), 4.18 (1H,
dd, J ) 13, 5.5 Hz), 4.55-4.70 (2H, m), 5.49 (1H, d, J ) 5.5
Hz), 6.22 (1H, s), 6.96 (1H, J ) 7.9 Hz), 7.00-7.40 (7H, m),
7.62 (1H, J ) 7.9 Hz); FAB-MS m/z 379 (MH+); Anal.
(C23H26N2O3‚‚0.6H2O) C, H, N.
trans-(3′R)-Quinuclidin-3′-yl 4-Hydroxy-1-phenyl-1,2,3,4-
tetrahydroisoquinoline-2-carboxylate (16c and 16d). A
mixture of 16c and 16d was prepared from trans-1-phenyl-
1,2,3,4-tetrahydroisoquinoline-4-ol (trans-29)20 by Method B
quantitatively.
16c: a colorless amorphous; [R]25 ) -165° (c ) 0.503,
D
1
EtOH); H NMR (DMSO-d6) δ 1.20-1.80 (4H, m), 1.85-1.95
(1H, m), 2.55-2.80 (5H, m), 3.05-3.15 (1H, m), 3.50 (1H, dd,
J ) 13, 3.7 Hz), 3.88 (1H, dd, J ) 13, 4.6 Hz), 4.60-4.70 (2H,
m), 5.16 (1H, d, J ) 6.1 Hz), 6.25 (1H, s), 7.10-7.35 (8H, m),
7.44 (1H, d, J ) 7.3 Hz); FAB-MS m/z 379 (MH+); Anal.
(C23H26N2O3) C, H, N.
g/cm3; Z value, 4.0; F000, 808; final R value, R ) 0.044, RW
0.062; goodness of fit indicator, 1.09.
)
Compound 16d was converted to the hydrobromide salt
(16e) and recrystallized from ethanol-diethyl ether for X-ray
crystallographic analysis. The absolute configuration is
1S,3′R,4S by the comparison of intensities of Bijvoet’s pairs.
Formula, C23H27N2O3Br; crystal system, orthorhombic; space
16d: a colorless amorphous; [R]25 ) +175° (c ) 0.500,
D
1
EtOH); H NMR (DMSO-d6) δ 1.25-2.00 (5H, m), 2.40-2.75
(5H, m), 2.90-3.05 (1H, m), 3.49 (1H, dd, J ) 13, 3.7 Hz), 3.87
(1H, dd, J ) 13, 4.9 Hz), 4.55-4.70 (2H, m), 5.18 (1H, d, J )

Muscarinic Receptor Antagonists
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 21 6605
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group, P212121; lattice parameters, a ) 13.350 (2) Å, b ) 17.437
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Molecular Modeling. The GASP module of SYBYL30 was
used to superpose the 1-phenyl-1,2,3,4-tetrahydroisoquinoline-
2-carboxylate derivatives. GASP parameters were set to the
following values: population size: 100, selection pressure: 1.1,
maximum number of operations: 60,000, operations incre-
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allele mutate weight: 96.0, full mutation weight: 0.0, full
cross-weight: 0.0.
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ceptor binding assays were performed in the reported
method24 with rat cortex, heart, and salivary glands using [3H]-
pirenzepine, [3H]-quinuclidinyl benzilate, and [3H]-N-methyl-
scopolamine as ligands for M1, M2, and M3 receptors, respec-
tively.
Rhythmic Contraction. Female Wistar rats were anes-
thetized with urethane (1.0 g/kg sc). The bilateral ureters were
ligated, then the urinary bladder was catheterized transure-
thrally and filled with saline to evoke reflex rhythmic contrac-
tions. After recording the peak intravesical pressure, com-
pounds were administered via the femoral vein cumulatively.
Fall in the pressure was measured in the period of 5-10 min
after each administration. A dose-response curve was ob-
tained in each rat and the dose required to reduce peak
intravesical pressure by 30% (ED30) was determined.
Salivary Secretion. Male Wistar rats were anesthetized
with urethane (1.2 g/kg i.p.). Compounds were administered
intravenously 15 min prior to injection of oxotremorine (0.8
µmol/kg iv). Saliva was collected by absorbent paper for 5 min
after the injection of oxotremorine.
Pressor. Effect on the pressor response caused by McN-
A343 was determined in pithed rats.24 Compounds were
administered intravenously 15 min before the injection of McN-
A343 (3 µmol/kg iv).
Bradycardia. Bradycardia was evoked in pithed rats by
intravenous injection of oxotremorine.24 Compounds were
administered 15 min prior to the challenge of oxotremorine.
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rightward by 10-fold (DR10) was calculated.
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hedron: Asymmetry 1997, 8, 2693-2695.
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Meldrum’s acid derivatives: Loss of chirality at the side of
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873.
Acknowledgment. We thank Dr. Yasuo Isomura,
presently at Mochida Pharmaceutical Co., Ltd., for
his efforts at Yamanouchi. We are grateful to Drs.
Toshiyasu Mase and Hiromu Hara for useful discus-
sions. We also thank Mr. Seiji Kobayashi, Dr. Minetake
Kitagawa, and Mrs. Masako Tateishi-Hirano for the
biological experiments, Mr. Hideaki Nakahara for X-ray
crystallographic analysis, Mrs. Yoko Yamagiwa-Yokota
for the superimposition study, and the members of the
Structure Analysis Research division, Yamanouchi Phar-
maceutical Co., Ltd., for NMR and mass spectral data
and elemental analysis.
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dihydro-2-oxo-1H-benzimidazole-1-carboxylic acid derivatives as
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Supporting Information Available: Elemental analysis
data of 9-16d and 39, and ORTEPII Drawings of 9e, 12c, 16c,
and 16e. This material is available free of charge via the
Internet at http://pubs.acs.org.
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